Krill is a small crustacean which lives in all the major oceans worldwide. For example, it can be found in the Pacific Ocean (Euphausia pacifica), in the Northern Atlantic (Meganyctiphanes norvegica) and in the Southern Ocean off the coast of Antarctica (Euphausia superba). Krill is a key species in the ocean as it is the food source for many animals such as fish, birds, sharks and whales. Krill can be found in large quantities in the ocean and the total biomass of Antarctic krill (Euphausia superba) is estimated to be in the range of 300-500 million metric tons. Antarctic krill feeds on phytoplankton during the short Antarctic summer. During winter, however, its food supply is limited to ice algae, bacteria, marine detritus as well as depleting body protein for energy. Virtue et al., Mar. Biol. 126, 521-527. For this reason, the nutritional values of krill vary during the season and to some extent annually. Phleger et al., Comp. Biochem. Physiol. 131B (2002) 733. In order to accommodate variations in food supply, krill has developed an efficient enzymatic digestive apparatus resulting in a rapid breakdown of the proteins into amino acids. Ellingsen et al., Biochem. J. (1987) 246, 295-305. This autoproteolysis is highly efficient also post mortem, making it a challenge to catch and store the krill in a way that preserves the nutritional quality of the krill. Therefore, in order to prevent the degradation of krill the enzymatic activity is either reduced by storing the krill at low temperatures or the krill is made into a krill meal.
During the krill meal process the krill is cooked so that all the active enzymes are denatured in order to eliminate all enzymatic activity. Krill is rich in phospholipids which act as emulsifiers. Thus, it is more difficult to separate water, fat, and proteins using mechanical separation methods than it is in a regular fish meal production line. In addition, krill becomes solid, gains weight and loses liquid more easily when mixed with hot water. Eventually this may lead to a gradual build up of coagulated krill proteins in the cooker and a non-continuous operation due to severe clogging problems. In order to alleviate this, hot steam must be added directly into the cooker. This operation is energy demanding and may also result in a degradation of unstable bioactive components in the krill oil, such as omega-3 fatty acids, phospholipids and astaxanthin. The presence of these compounds make krill oil an attractive source as a food supplement, a functional food product, and a pharmaceutical for the animal and human applications.
Omega-3 fatty acids have been shown to have potential effect of preventing cardiovascular disease, cognitive disorders, joint disease and inflammation-related diseases such as rheumatoid arthritis and osteoarthritis. Astaxanthin is a strong antioxidant and may also assist in promoting optimal health.
Published PCT Application No. WO 00/23546 discloses isolation of krill oil from krill using solvent extraction methods. Krill lipids have been extracted by placing the material in a ketone solvent (e.g., acetone) in order to extract the lipid soluble fraction. This method involves separating the liquid and solid contents and recovering a lipid rich fraction from the liquid fraction by evaporation. Further processing steps include extracting and recovering by evaporation the remaining soluble lipid fraction from the solid contents by using a solvent such as ethanol. The compositions produced by these methods are characterized by containing at least 75 μg/g astaxanthin, preferably 90 μg/g astaxanthin. Another krill lipid extract disclosed contained at least 250 μg/g canastaxanthin, preferably 270 μg/g canastaxanthin.
Published PCT Application No. WO 02/102394 discloses methods of treating and/or preventing cardiovascular disease, rheumatoid arthritis, skin cancer, premenstrual syndrome, diabetes, and enhancing transdermal transport. The methods include administering a krill or marine oil to a patient. The application also describes a test that was carried out to evaluate the effects of krill and/or marine oils on arteriosclerotic coronary artery disease and hyperlipidemia, and resulted in a cholesterol decrease of about 15%, a triglyceride decrease of about 15%, an HDL increase of about 8%, an LDL decrease of about 13%, and a cholesterol:HDL ratio decrease of about 14%
Published PCT Application No. WO 2007/080515 discloses a marine lipid extract derived from krill. The extract can be used in methods for preventing or treating thrombosis.
Korean Published Application No. 2006008155 discloses an oral composition comprising a mixture of glucosamine and krill oil (provided in a ratio of 2:3) for use in methods of inhibiting osteoarthritis.
U.S. Pat. No. 7,666,447 discloses compositions including krill extracts and conjugated linoleic acid. The compositions are used in methods for treating an individual having a disease state selected from the group consisting of a joint ailment, PMS, Syndrome X, cardiovascular disease, bone disease and diabetes. The methods comprise administering to the individual a therapeutically effective amount of a composition including conjugated linoleic acid and a krill extract comprising krill oil.
However, there remains a need in the art for methods of using compositions comprising krill oil to treat risk factors for metabolic, cardiovascular, and inflammatory disorders.